Edge connector with polarizing member

ABSTRACT

A connector having a socket for receiving the leading edge of a printed circuit board includes a polarizing and keying member adapted to engage an indexing slot adjacent the printed circuit board leading edge in a given direction. The engaging keyingindexing member and slot are disposed in the socket intermediate the socket bottom and the contact region of a contact element, permitting the contact element and the indexing-keying means to be aligned in the given direction.

[72] Inventor Bernard Silverstein Philadelphia, Pa. [21] Appl. No. 878,688 [22] Filed Nov. 21, 1969 [45] Patented Oct. 19, 1971 [73] Assignee lRCA Corporation [54] EDGE CONNECTOR WITH POLARIZING MEMBER 17 Claims, 11 Drawing Figs.

[52] 1.1.8. Cl 339/186 M, 339/17 L [51] lnt.Cl ..H01r 13/64, HOSk 1/07 [50] Field of Search 339/17 F, 17 L, 17 LC, 17 LM,176 MP, 176 MF,184, 186

[56] References Cited UNITED STATES PATENTS 2,765,450 10/1956 Richardson 339/192 3,492,538 1/1970 Fergusson 317/101 3,518,620 6/1970 Busheyetal 339/184 FOREIGN PATENTS 882,698 11/1961 GreatBritain 339/176 Primary Examiner-Marvin A. Champion Assistant Examinerl.awrence J. Staab Alt0rneyEdward J. Norton ABSTRACT: A connector having a socket for receiving the leading edge of a printed circuit board includes a polarizing and keying member adapted to engage an indexing slot adjacent the printed circuit board leading edge in a given direction. The engaging keying-indexing member and slot are disposed in the socket intermediate the socket bottom and the contact region of a contact element, permitting the contact element and the indexing-keying means to be aligned in the given direction.

PATENTEUUEHQIQYI 3061 sum 10F 4 INVEN'IOR.

Bernar Silverstein TORNE Y PATENTED I]!!! 1 9 IBYI SHEET 2 OF d 20 F ZO INVIiN'l ()R Bernard Siilverstez'n Fig. 6.

ATTORNEY PATENTEUDBHQIBY: 3,614,714

SHEET 4 UF 4 Fig. 199

INVIEN'I R,

By Bernard Szlverstem 26mm W ATTORNEY IEIIIGIE CGNNEGIFGM Wllllll-ll IGILAMING MEMIBIEFI The present invention relates to means for indexing and keying an edge connector with respect to a printed circuit board.

Connectors used for printed circuit board applications generally have a plurality of contact elements secured in elongated sockets adapted to receive an edge of a printed circuit board. The socket and circuit board arrangements are such that any one connector is adapted to receive a plurality of printed circuit boards, each board having a different circuit arrangement thereon. Consequently, to prevent mating an incorrect circuit board to a particular connector, means have been employed for keying a circuit board to a connector and for polarizing the circuit board to that connector. When so keyed, the circuit board conductors register with the connector contact elements only when the board and connector are coupled in a predetermined arrangement.

These keying means include a variety of configurations, one of which comprises keying tabs bridging the connector channel and longitudinally spaced along the channel between ad jacent pairs of opposed contact elements. This arrangement requires keying slots for these tabs to be preformed into the connector housing intermediate all of the contact element pairs to permit a keying tab to be inserted in any desired keying slot or slots. The circuit board usually has an index slot at an edge thereof adapted to receive the keying tab when the board is inserted into the connector in the correct orientation.

Other indexing means include keying members inserted into connectors adjacent various predetermined contact elements detachably secured to the contact elements. Another arrangement includes removing one or more contact elements and substituting a keying member in the void left by the removed contact element. In all of these arrangements, the keying member either takes up valuable contact space adjacent to the contacts, decreasing the number of possible contacts used in a given length of a connector. In none of these arrangements, may connectors of the type having staggered opposed contacts be utilized.

It is an object of the present invention to provide an edge connector with keying-indexing members which are adaptable for use with staggered contact connectors and which permit maximum utility of contact elements in a connector of a given size.

As herein described, an edge connector for a printed circuit board includes keying means adapted to engage indexing means in the printed circuit board in a given direction, the indexing and keying means engage each other over a predetermined depth in the given direction. Contact elements extending out from the connector body register with corresponding ones of printed circuit board conductors when the keying and indexing means are engaged. The contact region between each contact element and the corresponding conductor are spaced from the circuit board insertion edge a predetermined distance, this distance being greater than the engagement depth for at least one of the conductors. The engagement depth is greater than the maximum displacement in the given direction between any conductor termination adjacent an edge of the circuit board and any contact region.

Further advantages and features of the present invention will be apparent from the following description taken in conjunction with the drawings, in which:

FIG. I is a plan view of a connector including a keying member therein, according to a first embodiment of the invention;

FIG. 2 is an elevation view of the connector of FIG. I illustrating the keying member therein;

FIG. 3 is an elevation view illustrating indexing and keying members for use with the connector of FIG. 2;

FIG. 4 shows an enlarged cross section of the connector of FIG. 2 illustrating a printed circuit board improperly indexed to a keying member;

FIG. 5 shows a cross section of the connector of FIG. 2 illustrating proper engagement of the indexing and keying means;

FIG. 6 is an elevation view of a connector having a keying member according to a second embodiment of the invention;

FIG. '7 shows a cross section of the connector of FIG. 6 illustrating the engaged condition of the indexing and keying means;

FIG. d is an elevation view illustrating a third embodiment of the invention, and indicating the relationship between the indexing and keying means; and

FIG. 9 is a perspective view of a connector including indexing and keying means according to a fourth embodiment of the invention;

FIGS. 10 and 1111 are diagrammatic illustrations which are useful in understanding the principles of the invention.

In FIG. Ml, a printed circuit board Mil is shown engaged with keying member 117. Keying member M7 is seated in the bottom of a channel in a connector, not shown. Member I17 has a keying projection 11%. Slot or recess M2 of the printed circuit board Mil is engaged with projection 11M. Contact fingers 120-1123, mounted on the connector housing, not shown, overlap and register with conductors Mit-Mh, respectively, on board M0. The slot M2 and projection llllb are engaged a depth x.

Contact region y is the registration area between each of fingers mil-I23 and the corresponding one of conductors lMlEi-lldb. Distance w is the maximum distance in the direction of arrow I between the terminated end I of any conductor and the contact region y between any contact finger and conductor. In FIG. 10, for example, the distance w corresponds to the maximum distance between contact region y of conductor M6 and the terminated edge I of conductor M5. The letter 2 corresponds to the distance between at least one contact region y and edge 1160 of board Mt). For example, in FIG. I0, 2 corresponds to the distance between contact region y of conductor M7 and the adjacent edge ltitli of the printed circuit board Mil.

In order that recess M2 may be randomly located along edge 160 such that any contact region y of any conductor may be in alignment above the recess in the direction of arrow 195, the contact region y for all conductors must be disposed at least a minimum distance 2 from the edge 1160 of the board. In FIG. I'll, as noted, contact region y of conductor M7 and contact finger I22 are aligned with recess M2 in the direction of arrow 195. To align any other contact region y of conductors lids-M8 with a recess such as recess M2, then distance 2 is a minimum distance for all the contact regions of the board. However, when recess M2 is disposed along edge 160 at a predetermined location such as that of FIG. 10, then contact region y of conductor M7 only need be located a minimum distance x from edge 160 of the board Mil.

As shown in FIG. ill, when board M0 is shifted in direction of arrow 197 such that recess M2 and projection I18 are not engaged, none of the contact fingers 1204123 are in registration with any of conductors HIS-M8. In this condition, edge 1160 of board M0 abuts edge 1107 of projection 1 l8 so that the conductors Mil-M8 are displaced a distance equal to engageable depth .1: in the direction of arrow 195. Thus, none of conductors MS-Md will contact any of the contact fingers -123 when recess M2 and projection llllb are not engaged. By maintaining the relationship w x z, keying member 1117 may be disposed in a connector channel bottom providing maximum contact utilization in a connector.

FIG. I shows a preferred embodiment of a connector 18 having a plurality of contact elements 20 arranged in staggered opposed spaced relation. This relation is illustrative only, as other arrangements will function equally well with the keying and indexing means to be hereinafter described. In the connector body 13), there is a socket or longitudinal channel 112 which is adapted to receive a printed circuit board edgewise.

FIG. 2 shows preferred keying member 17 disposed at the bottom of the channel 12, adjacent bottom wall ill. The keying member 17 may preferably comprise a rigid insulating material. Keying member I7 includes a base portion 116 which may be an elongated member adapted to be closely received into channel 12. Extending from base portion 16 are one or more keying projections 18.

As shown in FIGS. 4 and 5, when member 17 is disposed in channel 12, portions 18 extend away from bottom wall 11, and are disposed intermediate contact region y of connector elements 20 and bottom wall 11. This arrangement permits the alignment in the direction of arrow 95 of both the keying portion 18 and a useful contact region y of contact element 20, which was not possible heretofore.

Keying member 17 of FIGS. 4 and 5 has projection 18 extending upwardly with respect to bottom wall 11 a distance x which distance is less from base wall 19 of member 17 than contact region y. Contact region y is that region which is in contact with conductor 45 of printed circuit board 40 when the board and the connector are properly engaged.

In FIG. 5, where the respective indexing and keying slots and members are shown engaged, conductor 45 is in registration with contact element 20. FIG. 4, however, shows the geometry associated with improper engagement of the indexing slot 42 to the keying projection 18. Note that in FIG. 4, edge 60 of board 40 abuts keying projection 18 at end 7, while in FIG. 5, edge 60 abuts base wall 19 of keying member 17. The engageable depth x is defined by the displacement in direction of arrow 95 of edge I of the conductors when displaced from the position as shown in FIG. 4 to the position as shown in FIG. 5. Thus, the engageable depth x is, in this in the length of projection 18 in direction 95. This depth, of course, will vary according to the particular lengths in direction 95 of the various indexing and keying means employed as related to the leading edge of a printed circuit board in the manner indicated.

Generally, the engageable depth is defined as that maximum distance the terminations t of printed circuit conductors adjacent a leading edge of a printed circuit board may be dis placed in a given direction when the associated indexing-keying male and female members adjacent the leading edge of a printed circuit board and the respective connector channel are in their respective abutting proper and improper engaged states. This maximum distance or engageable depth must be greater than the distance w between any contact region y and conductor termination of any conductor 45. In addition, contact region y of any conductor aligned with recess 47 is further from edge 60 than that distance defined by engageable depth x as indicated above. When these conditions are met, then the indexing and keying means may be disposed in alignment with the contact region between any contact element 20 and any conductor 45 without inhibiting the function thereof. By maintaining these relationships, none of the contact elements will register with any of the conductors 45 of the printed circuit board except when the board is correctly inserted in the connector channel.

In the illustrations of FIGS. 1 through 5, the keying member 17 has been shown to be a separate detachably secured member. In FIGS. 4 and 5, member 17 is disposed below the contact region y. When board 40 is removed from the channel, the contact element resiliently springs over member 17 retaining the member in the channel. However, this arrangement is illustrative only, as other variations could be devised which maintain the relationships described.

One such variation is shown in FIG. 6. In this embodiment, body 50 has a channel 12 similar to that in the connector of FIG. 1. However, disposed in the bottom wall 52 of the channel are a plurality of spaced recesses 31 which may be circular holes extending downwardly from bottom wall 52 of body 50 in the given direction of arrow 95. Each of recesses 31 is adapted to closely receive a keying projection 30 which may be a conventional pin made of metal or other rigid material pressed fitted therein.

According to the predetermined keying arrangement of FIG. 6, two pins 30 are shown, but any combination could be used.

FIG. 7 is an enlarged cross section of the connector of FIG. 6 in which keying member pin 30 is shown closely received in recess 31. The pin 30 extends upwardly a distance x from bottom wall 52. Distance x is the engageable depth between recess 42 of printed circuit board 40 and pin 30. Note the clearance space 71 between the upper end of pin 30 and the surface 75 of recess 42, caused by edge 60 of the circuit board abutting base wall 52. In this case, engageable depth x is determined by the upwardly extending position 49 of pin 30. Contact region y of FIG. 7 is shown spaced above bottom wall 52 the distance 2 defined above. In addition, distance w between terminated edge t of conductor 45 and contact region y is less than the engageable depth x, also as defined above.

In FIG. 8, another variation is shown. Connector 41 of FIG. 8 has a keying projection or male member 70 extending upwardly from the bottom wall 31 thereof. Tab 70 is equivalent to keying projection 18 of FIGS. 1 5. Contact elements 20 and conductor 45 each have a contact region y spaced from the keying member 70 and indexing slot 42, respectively, by a distance d. The keying member 70 is adapted to engage indexing slot 42 of the printed circuit board 40 in direction of arrow 95. The engageable depth between indexing slot 42 and keying member 70 is distance x, x being that engageable distance in the given direction of arrow 95. Each contact region y of any conductor 45 on the printed circuit board 50 is spaced in the given direction a predetermined distance w to an edge t of any conductor 45 which terminates adjacent the leading edge 60 of the printed circuit board 40. Again, this distance w is less than engageable depth 1:, and, contact region y on the circuit board is spaced from the leading edge 60 of the circuit board the distance 2,. This distance z, the sum of distances d and x, is greater than the engageable depth x for all contact regions y since, in this case, all contact regions y of the conductors lie along the same line equidistant from the edge 60.

Keying member 70 of FIG. 8 terminates at end 7 a distance intermediate contact region y and the bottom wall 31. Further, keying member 70, as are the keying projections of the above-described embodiments, may be disposed along longitudinal axis a of the channel regardless of the longitudinal position A of any contact element. As shown, keying member 70 may occupy any space along the longitudinal a axis in alignment with contact region y of any element 20 in the direction of arrow 95.

By disposing keying members adjacent to a bottom wall 11, 52 or 31 of the channel 12 of the connectors of FIGS. 2, 6, and 8, respectively, and intermediate contact region y of the contact region y of any element 20 in the direction of arrow 95.

By disposing keying members adjacent to a bottom wall 11, 52 or 31 of the channel 12 of the connectors of FIGS. 2, 6, and 8, respectively, and intermediate contact region y of the contact elements and the bottom wall, loss of utilization of any contact element is avoided, and, in addition, maximum utility of the longitudinal spacing of contact elements is ensured. Thus, greater flexibility and increased contact element density can be provided while maintaining maximum circuit protection.

As shown in FIG. 9, a fourth embodiment includes a keying member such as elongated female member 97 having a slot 96, and indexing male member, such as stud 95. In this case, the engageable depth is the maximum displacement of edge t of the conductors 45 of board 65 in direction of arrow when stud 95 abuts surface 98 of member 97 in the improper keyed state and when stud 95 is inserted in slot 96 in the proper state. In any case, the keying member, whether male or female, may be permanently or detachably secured to the connector adjacent the bottom channel wall thereof.

What is claimed is:

1. An edge connector for a printed circuit board, said board including indexing means adjacent an edge thereof, and a plurality of conductors disposed on a surface of the board, each conductor terminating adjacent said edge, said connector comprising:

a connector body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, and

a corresponding plurality of contact elements extending outwardly from said body and positioned to register with corresponding ones of said conductors when the keying and indexing means are engaged, the contact region between each contact element and the corresponding conductor being spaced a predetermined distance from said edge, said distance being greater than said engagement depth for at least one of said conductors, said one conductor being aligned with said indexing means in said given direction,

said engagement depth being greater than the maximum displacement in said given direction between any conductor termination and any contact region.

2. The connector of claim ll, wherein said connector body includes a socket for receiving a printed circuit board edgewise therein, the socket having a bottom wall and a sidewall depending therefrom, and

said keying means includes a keying member in communication with said socket intermediate said bottom wall and said contact region,

said contact elements extending outwardly from said sidewall over said bottom wall and said keying member such that said contact region is spaced from said bottom wall a distance greater than said engagement depth, said contact elements retaining said keying member in said socket.

3. The connector of claim 2, wherein said sidewall and bottom wall define a channel and wherein said keying member includes a base portion and a keying portion, said base portion being disposed within said channel adjacent said bottom wall, said keying portion being disposed facing said outwardly extending contact elements in said given direction, said indexing and keying means including complimentary male and female portions.

41. The connector of claim 3 wherein said keying portion comprises a male projection extending into said channel in said given direction, and

said base portion comprises an elongated member adapted to be closely received in said channel, said projection extending therefrom, said base portion being spaced from said contact region a distance greater than said engagement depth.

5. The connector of claim 2, wherein said bottom wall includes a recess in communication with said channel, and said keying member includes a male projection closely received by said recess and extending from said bottom wall toward said contact region in said given direction.

05. The connector of claim 2, wherein said keying member includes a plurality of spaced male projections extending therefrom toward said contact region in said given direction.

7. The connector of claim 2, wherein said keying member includes a male projection extending from said bottom wall toward said contact region.

8. The connector of claim 2;, wherein said given direction is defined by the direction of insertion of said printed circuit board into said socket.

9. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on a surface of the board, each conductor terminating adjacent said edge, said connector comprising:

a connector body including keying means capable of engaging said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, said indexing and keying means including complirnentary male and female members, and

a contact element extending outwardly from said body and positioned to register with at least one corresponding conductor only'when the keying and indexing means are engaged, the contact region between a contact element and its corresponding conductor being spaced a predetermined distance from said edge, said distance being greater than said engagement depth, for at least one of said conductors,

said engagement depth being greater than the maximum displacement in said given direction between any conductor termination and the contact region between said contact element and its corresponding conductor.

ill. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on at least one surface of the board, each conductor terminating adjacent said edge, said connector comprising:

a connector body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, and

a plurality of contact fingers secured to said body, each finger registering with and corresponding to a different one of said terminating conductors and arranged in overlapping relationship with its respective corresponding conductor such that each finger extends over the circuit board a predetermined distance from said edge when the indexing and keying means are engaged, the contact re gion between at least one of said fingers and said conductors being spaced a distance further from said edge than said engagement depth,

said engagement depth and the maximum displacement in said given direction between any conductor termination and any contact region being related such that each conductor contacts only its corresponding finger solely when the indexing and keying means are engaged while none of said conductors contacts any of said fingers when said indexing and keying means are unengaged.

ill. The connector of claim Ml, wherein said engagement depth is greater than the maximum displacement in said given direction between any conductor termination and any contact region.

12. The connector of claim illl, wherein said connector body defines an elongated U-shaped channel having a bottom wall and a sidewall,

each of said contact fingers being secured to said body such that the contact region thereof communicate with said channel over said bottom wall,

said keying means includes a keying member secured in said channel intermediate said bottom wall and said contact region.

H3. The connector of claim i2, wherein said bottom wall has a hole therein; which hole closely receives said keying member, said keying member including a male keying projection extending from said member toward said contact region.

114. The connector of claim it), wherein said connector body defines an elongated U-shaped channel having a bottom wall and two sidewalls,

each of said contact fingers being secured to said body such that the contact region thereof communicates with said channel over said bottom wall,

said keying means includes a female keying member having a slot therein parallel to said given direction and communicating with said channel, said female keying member being adapted to be received in said channel adjacent one of said sidewalls and said bottom wall.

115. An edge connector for a printed circuit board, said board including indexing means adjacent an edge thereof, and a plurality of conductors disposed on a surface of the board, said connector comprising:

a connector body having a channel adapted to receive the edge of said circuit board,

a corresponding plurality of contact elements extending outwardly from said body toward said channel each element being positioned to register with a corresponding one of said conductors, and p a keying member disposed in said channel solely between (i) the contact region between at least one contact eledexing means at an edge thereof and a plurality of conductors disposed on at least one surface of the board, each conductor terminating adjacent said edge, said connector comprising:

a connector body defining an elongated U-shaped channel having a bottom wall and two sidewalls, said body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, said keying means including a female keying member having a slot ment and the corresponding conductor and (ii) the channel bottom, said keying member being further disposed at any randomly designated location intermediate the ends of said channel.

16. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on at least one surface of the board, each conductor terminating adjacent said edge, said connector comprising:

a connector body including keying means adapted to en- 8 2 sflid indexing means in a given K Said f f 10 therein parallel to said given direction and being adapted g f il other over a Predemmmed depth m Sad to be received in said channel adjacent one of said an sidewalls and said bottom wall, and g y 9 q g fi secured f; said gl'f a plurality of contact fingers secured to said body, each g t F an mg to finger registering with and corresponding to a different f zif g fi i gggs ifig g zg pzg z zgff gggggg one of said terminated conductors and arranged in overlapping relationship with its respective corresponding g g g i s? gngerfextendzovgr a conductor such that each finger extends over the circuit z zg g iifiz z 2:: :32;: 3 2 2;; board a predetermined distance from said edge when the gion between at least one of said fingers and said conducggz g izi 23225233; 23 5525; :2: gzg gzg iizzpa further from sald edge than tors being spaced a distance further from said edge than said engagement depth and the maximum displacement in said depth each of Said Contact "3 being said given direction between any conductor termination Secured stald gg sachhthat i and any contact region being related such that each con- 25 .i i 5 3 if" Sal wa ductor contacts only its corresponding finger solely when Sal f p an e max'mum acelilen. m the indexing and keying means are engaged, said given direction between any conductor tennination said engagement depth being greater than the maximum disand any Contact 9" bemg sf f that T placement in said given direction between any conductor P on y lts correspon mg so e y w en terminafion and any Contact region the indexing and keying means are engaged. 17. An edge connector for a printed circuit board having in- 

1. An edge connector for a printed circuit board, said board including indexing means adjacent an edge thereof, and a plurality of conductors disposed on a surface of the board, each conductor terminating adjacent said edge, said connector comprising: a connector body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, and a corresponding plurality of contact elements extending outwardly from said body and positioned to register with corresponding ones of said conductors when the keying and indexing means are engaged, the contact region between each contact element and the corresponding conductor being spaced a predetermined distance from said edge, said distance being greater than said engagement depth for at least one of said conductors, said one conductor being aligned with said indexing means in said given direction, said engagement depth being greater than the maximum displacement in said given direction between any conductor termination and any contact region.
 2. The connector of claim 1, wherein said connector body includes a socket for receiving a printed circuit board edgewise therein, the socket having a bottom wall and a sidewall depending therefrom, and said keying means includes a keying member in communication with said socket intermediate said bottom wall and said contact region, said contact elements extending outwardly from said sidewall over said bottom wall and said keying member such that said contact region is spaced from said bottom wall a distance greater than said engagement depth, said contact elements retaining said keying member in said socket.
 3. The connector of claim 2, wherein said sidewall and bottom wall define a channel and wherein said keying member includes a base portion and a keying portion, said base portion being disposed within said channel adjacent said bottom wall, said keying portion being disposed facing said outwardly extending contact elements in said given direction, said indexing and keying means including complimentary male and female portions.
 4. The connector of claim 3 wherein said keying portion comprises a male projection extending into said channel in said given direction, and said base portion comprises an elongated member adapted to be closeLy received in said channel, said projection extending therefrom, said base portion being spaced from said contact region a distance greater than said engagement depth.
 5. The connector of claim 2, wherein said bottom wall includes a recess in communication with said channel, and said keying member includes a male projection closely received by said recess and extending from said bottom wall toward said contact region in said given direction.
 6. The connector of claim 2, wherein said keying member includes a plurality of spaced male projections extending therefrom toward said contact region in said given direction.
 7. The connector of claim 2, wherein said keying member includes a male projection extending from said bottom wall toward said contact region.
 8. The connector of claim 2, wherein said given direction is defined by the direction of insertion of said printed circuit board into said socket.
 9. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on a surface of the board, each conductor terminating adjacent said edge, said connector comprising: a connector body including keying means capable of engaging said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, said indexing and keying means including complimentary male and female members, and a contact element extending outwardly from said body and positioned to register with at least one corresponding conductor only when the keying and indexing means are engaged, the contact region between a contact element and its corresponding conductor being spaced a predetermined distance from said edge, said distance being greater than said engagement depth, for at least one of said conductors, said engagement depth being greater than the maximum displacement in said given direction between any conductor termination and the contact region between said contact element and its corresponding conductor.
 10. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on at least one surface of the board, each conductor terminating adjacent said edge, said connector comprising: a connector body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, and a plurality of contact fingers secured to said body, each finger registering with and corresponding to a different one of said terminating conductors and arranged in overlapping relationship with its respective corresponding conductor such that each finger extends over the circuit board a predetermined distance from said edge when the indexing and keying means are engaged, the contact region between at least one of said fingers and said conductors being spaced a distance further from said edge than said engagement depth, said engagement depth and the maximum displacement in said given direction between any conductor termination and any contact region being related such that each conductor contacts only its corresponding finger solely when the indexing and keying means are engaged while none of said conductors contacts any of said fingers when said indexing and keying means are unengaged.
 11. The connector of claim 10, wherein said engagement depth is greater than the maximum displacement in said given direction between any conductor termination and any contact region.
 12. The connector of claim 10, wherein said connector body defines an elongated U-shaped channel having a bottom wall and a sidewall, each of said contact fingers being secured to said body such that the contact region thereof communicate with said channel over said bottom wall, said keying means includes a keying member secured in said channel intermediate said bottom wall and said contact region.
 13. The connector of claim 12, wherein said bottom wall Has a hole therein; which hole closely receives said keying member, said keying member including a male keying projection extending from said member toward said contact region.
 14. The connector of claim 10, wherein said connector body defines an elongated U-shaped channel having a bottom wall and two sidewalls, each of said contact fingers being secured to said body such that the contact region thereof communicates with said channel over said bottom wall, said keying means includes a female keying member having a slot therein parallel to said given direction and communicating with said channel, said female keying member being adapted to be received in said channel adjacent one of said sidewalls and said bottom wall.
 15. An edge connector for a printed circuit board, said board including indexing means adjacent an edge thereof, and a plurality of conductors disposed on a surface of the board, said connector comprising: a connector body having a channel adapted to receive the edge of said circuit board, a corresponding plurality of contact elements extending outwardly from said body toward said channel each element being positioned to register with a corresponding one of said conductors, and a keying member disposed in said channel solely between (i) the contact region between at least one contact element and the corresponding conductor and (ii) the channel bottom, said keying member being further disposed at any randomly designated location intermediate the ends of said channel.
 16. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on at least one surface of the board, each conductor terminating adjacent said edge, said connector comprising: a connector body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, and a plurality of contact fingers secured to said body, each finger registering with and corresponding to a different one of said terminating conductors and arranged in overlapping relationship with its respective corresponding conductor such that each finger extends over the circuit board a predetermined distance from said edge when the indexing and keying means are engaged, the contact region between at least one of said fingers and said conductors being spaced a distance further from said edge than said engagement depth, said engagement depth and the maximum displacement in said given direction between any conductor termination and any contact region being related such that each conductor contacts only its corresponding finger solely when the indexing and keying means are engaged, said engagement depth being greater than the maximum displacement in said given direction between any conductor termination and any contact region.
 17. An edge connector for a printed circuit board having indexing means at an edge thereof and a plurality of conductors disposed on at least one surface of the board, each conductor terminating adjacent said edge, said connector comprising: a connector body defining an elongated U-shaped channel having a bottom wall and two sidewalls, said body including keying means adapted to engage said indexing means in a given direction, said means engaging each other over a predetermined depth in said direction, said keying means including a female keying member having a slot therein parallel to said given direction and being adapted to be received in said channel adjacent one of said sidewalls and said bottom wall, and a plurality of contact fingers secured to said body, each finger registering with and corresponding to a different one of said terminated conductors and arranged in overlapping relationship with its respective corresponding conductor such that each finger extends over the circuit board a predetermined distance from said edge when the indexing and keying means are engageD, the contact region between at least one of said fingers and said conductors being spaced a distance further from said edge than said engagement depth, each of said contact fingers being secured to said body such that the contact region thereof communicates with said channel over said bottom wall, said engagement depth and the maximum displacement in said given direction between any conductor termination and any contact region being related such that each conductor contacts only its corresponding finger solely when the indexing and keying means are engaged. 